SARS has killed a 14th Canadian and infected a new cluster of Toronto hospital workers even though they were protected from head-to-toe in gowns, gloves, masks and eye shields.

The latest cluster has heightened concerns the mysterious Severe Acute Respiratory Syndrome virus can be spread via objects, in addition to face-to-face contact, and can remain potent on objects for much longer than previously believed.

Also, one expert predicted yesterday that SARS is likely to remain in Canada -- despite the current battle to contain it -- because people will continue to "import" it from lesser developed countries.

The latest Canadian death was a 99-year-old man who succumbed Friday, according to an Ontario government news release that provided no further details.

The previous 13 SARS deaths have all been in the Toronto area. Most have been elderly with underlying health problems, but experts are increasingly worried the virus is now making younger, otherwise healthy people critically ill.

The new cluster erupted at Sunnybrook and Women's College Health Sciences Centre in suburban Toronto, which has treated about half the region's SARS patients over the past month. It has 20 to 25 of them admitted at any given time.

As of yesterday, four staff members, including at least one doctor, a nurse and a respiratory therapist, were in hospital and almost certainly have SARS.

Another eight hospital staff members were sent into home quarantine as potential SARS cases.

A Vancouver hospital also isolated one of its wards yesterday when a nurse who worked there was identified as a possible SARS case.

Officials said they believe the Sunnybrook infections occurred during difficult intubations, including one last Sunday that took four hours. Intubation involves placing a tube down a patient's throat to facilitate breathing.

Both patients are now believed to be "super spreaders," or viral shedders, who are much more infectious than average SARS patients.

Some staff started feeling symptoms associated with SARS on Wednesday and Thursday. Senior hospital staff became aware of the threat late Thursday night.

Dr. Mary Vearncombe, the hospital's head of infection, prevention and control, said one worker's eye shield slipped during the Sunday intubation procedure, but there is no other known breach of the staff's "full-droplet" protection.

That includes gowns, gloves, eye shields and N-95 masks.

"We were using what both Health Canada and the (Atlanta-based) Centers for Disease Control consider to be maximal precautions for these patients," she said, adding it's possible some potentially infected staff was not present at the intubations.

That raises serious questions about how the virus was spread and whether the current precautions are enough to protect health care workers.

"We're examining everything we do and we're looking at a number of different options in terms of making that particular procedure safer for the health care workers," she said. One option is anesthetizing patients for intubation to reduce saliva spread.

Dr. Andrew Simor, the hospital's head of microbiology, said the virus continues to surprise the experts.

"We know that the (precautionary) measures that have been recommended should be adequate to deal with those (patients) but we're also impressed with just how easily the virus is spread, how it might contaminate the environment," he said.

Dr. Simor added that, in a Friday night conference call with Health Canada and the Centers for Disease Control and Prevention, a CDC expert surprised the others by revealing that the virus can remain potent on objects much longer than previously thought.

"What the CDC mentioned to us last night was that, in their studies, they found that you could still culture viable virus from surfaces after as much as 24 hours, which is longer than we normally expect viruses to be able to survive in the environment," he said.

In a statement yesterday, the World Health Organization said it is also concerned about the possibility of environmental transmission. It's looking closely at how SARS spread through a Hong Kong apartment complex, linked to the building's sewage system which carried the virus from an infected person.

However, the health body concluded there is "little risk" that environmental causes are behind a probable SARS case in a Toronto condominium which health officials have not been able to directly link to a SARS-infected family in the same building. The incubation period has passed with no further cases, the WHO noted.

The WHO is closely watching a disturbing trend in Hong Kong and Canada where SARS is striking younger, healthier people with greater ferocity. In particular, it is watching efforts to contain an outbreak among a 500-member, Toronto-area Catholic prayer group. Twenty-nine of them were infected, some of whom are not old or ill.

"The outbreak is regarded as a test case of whether rigorous contact tracing and other stringent public health measures can contain further spread even when very large numbers of persons may have been exposed," the WHO said.

Dr. Simor said he has seen the disturbing trend first-hand.

"The experience in Hong Kong has been a larger number of younger adults getting very severe illness, sometimes fatal," he said. "We are beginning to see that in Toronto as well."

The new cluster will further tax Toronto's almost-paralysed health care system. Instead of easing operating restrictions as it had planned, Sunnybrook has effectively closed its critical care, cardiovascular intensive care and SARS units for 10 days as a precaution.

"It's a huge burden on the system,'' said Leo Steven, the hospital's chief executive, adding that Sunnybrook, probably the biggest trauma centre in Canada, will now have to send trauma patients to other hospitals in Toronto, Hamilton and beyond.

Dr. Vearncombe predicted that even if containment measures are successful, Canada will have to learn to live with the SARS threat.

"I have some level of optimism that we can contain it in Toronto," she told reporters. "I have no optimism that we can contain it in developing areas of the world like mainland China so we will continue to import cases and we're going to have to remain absolutely vigilant."

Canada has about 300 probable and suspect cases of SARS in six provinces, mostly in Ontario.